Refrigeration – Automatic control – Selective heating or cooling
Reexamination Certificate
1999-05-26
2001-01-30
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Selective heating or cooling
C062S197000, C062S196400, C062S228500, C062S513000
Reexamination Certificate
active
06178761
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to air conditioning apparatus. In particular, the invention is directed to air conditioning apparatus, especially for the cabin of a vehicle, in which the apparatus includes: an air conditioning loop for the flow of a refrigerant fluid therein, the loop containing a compressor which is arranged to receive the refrigerant fluid in the gaseous state and to compress it to a supercritical pressure; a first heat exchanger which is adapted to cool the fluid compressed by the compressor at a substantially constant pressure, by transferring heat from a first external medium to the fluid; a first expansion device which is adapted to reduce the pressure in the fluid leaving the first heat exchanger, so as to put at least some of the fluid in the liquid state; and an evaporator which is arranged to change the state of the fluid received from the first expansion device from the gaseous state to the liquid state at a substantially constant pressure, by taking heat from a second external medium for the purpose of cooling the space (for example the cabin of a vehicle) which is to be air conditioned. The fluid thus vaporised is then aspirated by the compressor.
BACKGROUND OF THE INVENTION
Forms of the apparatus of the above general type are described for example in the specifications of International Patent Publication No. WO93/06423, U.S. Pat. No. 5,245,836 and U.S. Pat. No. 5,291,941. The refrigerant fluid used in these apparatuses is typically carbon dioxide (CO
2
).
Where it is not required to cool the air which is to be delivered into the cabin of a vehicle, but merely to heat the air, it is usual to utilize the heat which is produced by the propulsion engine of the vehicle, for example by passing air in contact with a heating radiator through which the engine coolant fluid flows. When the engine is cold, no heat can be drawn from it for the purpose of heating the cabin. This results in a considerable delay before the cabin can be brought to the required temperature, and is consequently detrimental to the comfort of the occupants of the vehicle. In some cases, the coolant liquid never, during the entire duration of a journey, reaches a high enough temperature to warm the occupants as they would wish.
In order to enable the cabin to be brought to the required temperature more quickly, various supplementary devices may be used, in particular those which involve the use of heaters or electrical radiators, but these are somewhat expensive.
DISCUSSION OF THE INVENTION
An object of the present invention is to enable a space, for example the cabin of a vehicle, to be heated more rapidly than hitherto when the engine is cold, or to increase the quantity of heat where the heat available is insufficient, without the need to provide of the any costly prior means for this purpose.
According to the invention, an air conditioning apparatus, especially for the cabin of a vehicle, includes for the flow of a refrigerant fluid therein, an air conditioning loop containing: a compressor adapted to receive the fluid in the gaseous state and to compress it to a supercritical pressure; a first heat exchanger arranged to cool the fluid compressed by the compressor at a substantially constant pressure, by transferring heat to a first external medium; a first expansion device adapted to reduce the pressure of the fluid leaving the first heat exchanger so as to put at least some of this fluid into the liquid state; and an evaporator to put into the gaseous state the fluid derived in the liquid state from the first expansion device, at a substantially constant pressure by taking heat from a second external medium for cooling the space to be air conditioned, with the fluid thus vaporised being subsequently aspirated by the compressor. The apparatus further includes a first bypass branch disposed in parallel with the first heat exchanger, switching means being provided for the purpose of causing the fluid to flow, as desired, in the first heat exchanger to constitute the air conditioning loop, or in the first bypass branch so as to constitute a heating loop in which the evaporator transfers heat from the refrigerant fluid to the second external medium for the purpose of heating the said space.
Preferably, the first expansion device serves to expand the fluid both in the air conditioning loop and in the heating loop. In other embodiments of the invention, the first expansion device serves to expand the fluid in the air conditioning loop, while the apparatus further includes a second expansion device which expands the fluid in the heating loop.
Where such a second expansion device is provided, it may be disposed at the output of the evaporator.
According to a preferred feature of the invention, a non-return valve is disposed between the output of the first heat exchanger and the upstream end of the first bypass branch.
According to another preferred feature of the invention, the air conditioning circuit further includes an internal heat exchanger which is adapted to transfer heat between two sections of the circuit which are common to both the air conditioning loop and the heating loop, the first said section situated between the downstream end of the first bypass branch and the first expansion device, the second said sections situated between the evaporator and the compressor.
The second expansion device may be disposed between the downstream end of the first bypass branch and the first section of the internal heat exchanger.
According to a further preferred feature of the invention, the apparatus further includes a second bypass branch which is arranged so as to be connected, by the said switching means, into the heating loop upstream of the evaporator, and this second bypass branch contains a second heat exchanger (not the internal heat exchanger mentioned above), which is also adapted to transfer heat from the refrigerant fluid to the second external medium for the purpose of heating the space.
Preferably then, the second bypass branch is arranged in parallel with the first expansion device, and contains the second expansion device upstream of the second heat exchanger.
The fluid flow switching means may include the first and second expansion devices, which prevent the flow of fluid to establish the heating loop and the air conditioning loop respectively.
The said second external medium is preferably a stream of air which is intended to be delivered into the space to be air conditioned. Preferably, the evaporator and the second heat exchanger are disposed in series in that order in the path of the flow of air.
A heat source external to the refrigerant fluid circuit is disposed in the path of the stream of air downstream of the evaporator, and if necessary downstream of the second heat exchanger.
Means may be provided for varying the thermal power transmitted from the heating loop to the second external medium. These means for varying thermal power are preferably adapted for the purpose of adjusting the first expansion device and/or the second expansion device. The means for varying the thermal power may constitute means for varying the capacity or the speed of the compressor.
In some embodiments of the invention, a reservoir is disposed in the air conditioning loop upstream of the compressor.
The various features and advantages of the invention will appear more clearly on a reading of the following detailed description of some preferred embodiments of the invention, which are given by way of non-limiting example only and with reference to the accompanying drawings, in which those elements which are identical or similar to each other are designated in all the Figures by the same reference numerals.
REFERENCES:
patent: 3421339 (1969-01-01), Volk et al.
patent: 5245836 (1993-09-01), Lorentzen et al.
patent: 5291941 (1994-03-01), Enomoto et al.
patent: 5685160 (1997-11-01), Abersfelder et al.
patent: 5694784 (1997-12-01), Frey et al.
patent: 197 25 978 (1998-01-01), None
patent: 93/06423 (1993-04-01), None
Morgan & Finnegan , LLP
Tanner Harry B.
Valeo Climatisation
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